1. Field of the Invention
The invention relates to signal processing apparatus, and more particularly, to an apparatus for processing an input signal to increase signal estimation accuracy.
2. Description of the Prior Art
In signal processing technique related fields, such as communication engineering, multimedia signal processing, medical engineering, etc., suitable processing and estimation of a received signal are required to efficiently and accurately extract signal parameters and information transmitted through an original signal corresponding to the received signal. Taking a communication system as an example, in order to acquire information transmitted from a transmitter, a receiver corresponding to the transmitter utilizes a signal processing technique to extract desired original information from a received signal having undergone interference caused by modulation, multi-path effects, channel fading, and additive noise, etc. Due to signal magnitude loss and estimation error in a signal processing procedure, however, information transmitted by the received signal is often unable to be recovered accurately.
A conventional complicated processing method is used to overcome the above-mentioned problem. When operation complexity is high, it is difficult to obtain real-time estimation of a received signal, increasing the implementation cost. Another conventional antenna diversity technique utilizes a plurality of antennas to receive a plurality of signals transmitted by the same remote signal source. After the received signals are processed and combined using appropriate combining methods (for example, equal gain combining, or maximum ratio combining), estimations are made based on a combined signal corresponding to the received signals. A lower bit error rate (BER) as well as a higher system performance of the communication system is achieved due to an at least partially independent channel fading effect of the received signals. Nevertheless, when a signal-to-noise ratio (SNR) of a specific received signal corresponding to a specific antenna is apparently higher than SNRs of the received signals corresponding to other antennas, the performance of the communication system will be approximately the same as the performance of performing signal estimations based on the specific received signal only. In this case, utilizing antenna diversity technique does not improve the performance of the communication system.